Histomorphological study on silver carp ovary in two age groups

Maturity of silver carp (Hypophthalmichthys molitrix) ovary takes place at 2-8 years old and it is depends on photoperiod and environmental water temperature. The aim of this study was to identify macroscopical and microscopical structure of silver carp ovary in two categories of body weight, total body length and at 2 and 4 years old in Khuzestan province climatic conditions. 20 silver carp ovaries were studied in two groups: Group 1(G1): 10 fish with total body length 46 ±1.33 Cm and weight 1050±0.09 grand approximately 2 years old. Group 2(G1): 10 fish with total body length 86±3.64 Cm and weight 5460±800 gr and approximately 4 years old. For the histometrical studies, 5-6 µ sections were made by routine paraffin embedding method and stained by H&E and PAS. Microscopic results showed that ovaries of G1 covered by a thin loose connective capsule which numerous of egg-bearingtrabecula extended from capsule into ovaries. These trabecula contained primary germ cells, oogonium, chromatin nocleolus, perinocleolus and cortical alveolus follicles. Ovaries of G1 do not have yolk and mature follicles. But in ovaries of G2, growth and mature follicles were observed and mature follicles were most follicles. Histometrical results showed that there are not a significant differences in diameter of follicles, oocytes and oocytes nucleolus in G1 and 2. The maximum and minimum diameter of follicles were seen in mature and chromatin nucleolus follicles respectively. The Zona plucida thickness was increased from corticalalveolus (1.53±1.11 mm) to mature follicles (6.88±0.21 mm) significantly (p<0.05). The most interesting finding of this study is that in Khuzestan Province climate, the ovary of silver carp fish in G1, with average weight 1050 ±0.09 gr and total length 46±1.33 Cm and approximately of 2 years old is immature but ovary of G2 with average weight of 5460± 800 gr and total length 86±3.64 Cm and approximately 4 years old is mature.